[Mi40793]

I have experience operating and maintaining TK42, TK27, and PC70. My opinion: For all the griping and rock-throwing, TK42’s, and TK27’s, delivered from 1965 worked, were very reliable overall, and had a stable color encoder. These first generation solid state cameras were in service many years.

TK42’s were noisy in color channels compared to later cameras due to the light split to the IO. Hard to even see the registration chart in the blue channel of the 42 for the noise. But produced good B&W with the 4.5 in IO. Yes, NBC rejected 42’s, kept running TK41’s in studios, and installed many PC-70’s on all their field trucks, except Burbank.

PC70 was very rugged, took abuse, stable circuit design. Three tube cameras had more light on color channels so that helped with chroma noise. Tradeoff for any 3 tube design was monochrome resolution due to any registration errors, relatively minor problem. PC70s used an image enhancer to improve apparent resolution, overall very acceptable pictures, and sold many cameras.

RCA caught up with the TK-44A. RCA had tried to make a small IO, the TK-44 ‘Isocon’, but production failed, so TK44A used plumbicons and RCA licensed the technology. Simplicity of a vidicon with sensitivity of an IO. Plumbs were good but not perfect, Amperex later years had trouble making good tubes. RCA and EEV did ok. A tough business. Solid state sensors were the breakthrough, pioneered for broadcast cameras. by RCA.

TK27 film camera was also reliable, as it used the same modules as the TK42. At one station I maintained five 27’s. RCA sold a lot of these starting 1965. Reliable, stable, not as good as later film cameras but many in network and local operation after 12-15 years. To accommodate film density variation TK27 used an auto-target voltage sensitivity method. Problem was tracking all vidicons together was virtually impossible, plus a characteristic ‘blooming’ on large scene brightness changes as target voltage changed. Solution was to lock the target voltages and use a variable density light wheel operating on the video level. Adding an image enhancer to the mono channel also improved the TK27 a lot.

Further, both the 42’s and 27’s originally had fixed gamma, RCA expected tube selection and neutral density filters at each vidicon to match gamma, very difficult. Later versions of TK27 and 42 video modules added gamma controls so you could adjust gray scale tracking on color channels.